1. Field of the Invention
2. Description of Related Art
Three basic methods for moving items used in subterranean wells, known as conveyance methods (CM) are:
Jointed Pipe (JP)xe2x80x94sections of pipe are screwed together at xe2x80x9cjointsxe2x80x9d to form a xe2x80x9cstringxe2x80x9d of pipe. JP includes drill pipe, production tubing and casing. Drill pipe and drill collars are used to form drill strings.
Coiled Tubing (CT)xe2x80x94continuous tubing or pipe which is coiled onto a reel at the surface, and spooled on and off the reel when being run in and out of a well.
Wireline (WL)xe2x80x94cable. There are several types of WL, including electric cable, braided cable, and xe2x80x9cslick-linexe2x80x9d.
Computer based models have been developed to calculate many quantities such as the forces, stresses, torques, stretch, etc. associated with these conveyance methods as the pipe, tubing or wireline are run into and out of subterranean wells. U.S. Pat. No. 5,044,198 gives a detailed description of one such model used for drilling. The known prior art, Orpheus software (commercially available from the owner of this invention) models all of these CM. Mathematical models or CMM""s (conveyance method models) refer to computer models for the various conveyance methods.
These known CMM""s take many parameters into consideration when performing calculations. The parameters may vary between the various CM. For example, JP and CT are pipes, so they may have internal pressure and fluid flow. WL has no internal flow path and thus does not have internal pressure and fluid flow. The following is a list of some of the parameters the CMM""s take into consideration:
Well propertiesxe2x80x94hole geometry, temperature and diameter versus the hole depth
Frictionxe2x80x94dynamic and static friction coefficients throughout the well
Pressuresxe2x80x94pressures inside and outside along the length of the well
Fluid propertiesxe2x80x94viscosity, density and flow rates of the fluids inside and outside of systems used in the CM
Material propertiesxe2x80x94strength and elastic modulus of the material the systems used in the CM are made of
Dimensions of CM systemsxe2x80x94inside and outside diameters along the length
Applied torques and forcesxe2x80x94torque and/or force applied at the downhole end of the CM system, and/or applied at the surface
Tool propertiesxe2x80x94length, outside diameter, stiffness, internal diameter, flow restrictions in the tools being conveyed by the CM system, if any
Speedsxe2x80x94axial speed and rate of rotation (RPM).
These known CMM""s are then used to determine many things such as:
When the CM system is approaching some limit at which it will break or buckle;
How much the CM system will stretch or shrink due to axial forces, helical buckling, temperature and pressure. This change in length is often needed to accurately calculate the depth of the end of the CM system or the location of the tools it is conveying;
How much force can the CM system apply at the downhole end of the tools, either in tension (as in pulling on a plug) or in compression (as in applying weight on bit (WOB)) while drilling;
How much torque is being applied at the downhole end when a certain amount of torque is applied at surface;
How much twist is in the CM system between the surface and the downhole end;
The torsional and axial dynamic frequencies for stick-slip type movements; and
The point at which the CM system is stuck in a well.
It is often desirable to run these CMM models in xe2x80x9creal-timexe2x80x9d. Measured parameters such as the force at surface (often called xe2x80x9chook loadxe2x80x9d for JP drilling or xe2x80x9cweightxe2x80x9d for CT and WL applications) and other parameters measured in real-time are input to the CMM, and it calculates the desired values such as a depth correction, WOB, etc. also in real-time. These calculated values are then displayed to those operating the system along with the measured parameters. Usually the display of updated values occur in less than 1 or 2 seconds, to be considered real-time. If dynamic effects are being considered, the real-time calculation must be even faster.
However, the CMM""s often require complicated calculations, e.g. numerically solving differential equations repeatedly. Due to the length and complexity of the calculations, the computer may not be able to perform these CMM calculations fast enough to perform real-time updates.
To avoid this problem, highly simplified CMM""s have been developed, such as the one in U.S. Pat. No. 6,026,912. Simplified CMM""s such as this can be run in real-time, but, are typically accurate for only certain specific cases such as vertical well drilling.
The present invention provides a method for complex CMM calculations to be made available in real-time. According to one aspect of the present invention a CMM includes a computer program that calculates desired output parameters for a range of input parameters ahead of time (e.g. several seconds or minutes ahead of real time, or before the operation begins) based upon the best data available at that time. If the CMM is being run only a short time (seconds or minutes ahead of time), actual current measured data is used. If the CMM is being run before the operation, the data will be estimated or predicted. The relationship between the input and output parameters is then modeled using a relatively simple mathematical model technique such as a curve-fit or data table technique. This simple mathematical model (SMM) technique includes a computer program that is then used in an appropriate computer to determine output parameters in real-time based upon the real-time input parameters.
Curve-fit techniques are known to those skilled in mathematics. There are many types of curve-fits. Given a series of n data points, (xj,yj), calculated by a CMM, where x is an input parameter and y is a calculated parameter, the equation of a line or curve is developed which passes through or close to these points. One common curve-fit is linear, taking the form of:
y=A+Bx
Where A and B are the curve fit constants. This curve-fit forms a linear SMM which calculates the output parameter y for a given input parameter x. It is much easier to calculate than the complex equations in a CMM.
A parabolic (second order polynomial) curve fit would take the form of:
y=A+Bx+Cx2
In this case A, B and C are the curve fit constants.
A hyperbolic curve-fit may be written in the form:
xe2x80x83y=A+B/(xxe2x88x92C)
There are many other types of curve-fits known to those skilled in mathematics including logarithmic, exponential, moving average, etc. Curve-fit techniques are known which allow multiple input parameters to be considered. Any suitable type of curve-fit may be used to create the SMM. The curve-fit constants may or may not have any physical significance (xe2x80x9cphysical significancexe2x80x9d means a constant is related to an actual physical parameter, e.g., but not limited to the buoyant weight of the WL in pounds per foot or density of drilling fluid in pounds per gallon).
With any curve-fit technique, there may be some error. In such a case an SMM will not produce exactly the same calculated result as a CMM. The type of curve-fit used in any specific application is chosen carefully to minimize this error. The curve-fit may, in certain aspects, be chosen at the time the SMM software is developed based upon an understanding of the usual shape of the curve, and thus the type of curve-fit which will most likely work well. Alternatively, multiple curve-fits are developed. For each curve-fit an error is calculated based upon the input data points. The curve-fit with the smallest error is then used for the SMM. Alternatively, multiple curve-fits are made available, and the operator chooses the curve-fit to be used in the SMM.
Alternatively, the n data points calculated by a CMM are placed in a data table available to the real-time software. The real-time software uses the data table and interpolates or extrapolates to obtain a desired value. In this case, the SMM is simply the equations used to interpolate or extrapolate. Interpolation and extrapolation are known to those skilled in mathematics.
It may be that multiple SMM""s are needed depending on some of the input parameters. For example, when running WL in and out of a deviated well it may be desirable to know the depth of the tools corrected for the change in length of the WL. In such a case one SMM may be used when the WL is being run into the hole (RIH), and a different SMM may be used when the WL is being pulled out of the hole (POOH). The real time software would first determine if the WL is being RIH or POOH, and would then use the appropriate SMM to calculate the depth correction.
Multiple SMM""s may be needed for different parameters. For example, in a drilling system a CMM may calculate both the torque on bits (TOB) and the WOB. However, one SMM may be used to calculate the real-time TOB, given the real-time surface torque, and another SMM may be used to calculate real-time WOB given the real-time hook load.
The SMM""s usually may not take all of the parameters into consideration. Instead, a CMM is run when necessary to update the SMM""s. For the above WL examples, the CMM takes the density of the fluid in the well into consideration because it affects the buoyancy of the CM system and tools. The SMM technique, in one aspect, has well fluid density as one of its input parameters, but this may make the SMM too complicated (to develop and/or to run in real-time. Multiple SMM""s are then developed for multiple fluid densities, and the real-time system then chooses the appropriate SMM based on current mud density. However, since the fluid density in the well does not change very rapidly, the CMM may be run from time to time to update the SMM""s for the most recent fluid density.
The basic steps employed in certain embodiments of a method according to the present invention are as follows:
1. A CMM is run for a plurality of points covering the expected range of the input parameters, and the output parameters are calculated.
2. SMM""s are developed which relate the calculated output parameters to the input parameters. These may be in the form of curve fitsxe2x80x94or data tables.
3. The real-time system obtains the real-time input parameters, and then uses the SMM""s to calculate the output parameters. Because the SMM""s are relatively simple to
4. Step 3 is repeated as fast as necessary for the application, providing a continuous real time display.
5. When a parameter (e.g. depth while drilling) not considered in the SMM""s changes significantly, or on a regular time interval, steps 1 and 2 are performed again, and the SMM""s are updated. This is performed in a background mode or on a different computer, so that the running of the CMM does not interfere with the real-time updating.
A real time system, according to the present invention, includes, in certain aspects, appropriate data acquisition devices (e.g. sensors), computer(s) with appropriate programming, real-time modeling programs, and real-time displays.
Certain embodiments of this invention are not limited to any particular individual feature disclosed here, but include combinations of them distinguished from the prior art in their structures and functions. Features of the invention have been broadly described so that the detailed descriptions that follow may be better understood, and in order that the contributions of this invention to the arts may be better appreciated. There are, of course, additional aspects of the invention described below and which may be included in the subject matter of the claims to this invention. Those skilled in the art who have the benefit of this invention, its teachings, and suggestions will appreciate that the conceptions of this disclosure may be used as a creative basis for designing other structures, methods and systems for carrying out and practicing the present invention. The claims of this invention are to be read to include any legally equivalent devices or methods which do not depart from the spirit and scope of the present invention.
The present invention recognizes and addresses the previously-mentioned problems and long-felt needs and provides a solution to those problems and a satisfactory meeting of those needs in its various possible embodiments and equivalents thereof. To one skilled in this art who has the benefits of this invention""s realizations, teachings, disclosures, and suggestions, other purposes and advantages will be appreciated from the following description of preferred embodiments, given for the purpose of disclosure, when taken in conjunction with the accompanying drawings. The detail in these descriptions is not intended to thwart this patent""s object to claim this invention no matter how others may later disguise it by variations in form or additions of further improvements.
What follows are some of, but not all, the objects of this invention. In addition to the specific objects stated below for at least certain preferred embodiments of the invention, other objects and purposes will be readily apparent to one of skill in this art who has the benefit of this invention""s teachings and disclosures. It is, therefore, an object of at least certain preferred embodiments of the present invention to provide:
New, useful, unique, efficient, nonobvious systems and methods for using complex CMM calculations in real-time for wellbore operations;
Such systems and methods which employ a relatively simple SMM technique (e.g. curve-fit technique or data table techniques) to determine output parameters in real-time;
Such systems and methods that use multiple SMM""s;
Such systems and methods in which a CMM is used periodically to update an SMM; and
Such systems that include data acquisition devices, computer(s) with suitable programming, and/or with real-time displays.
Certain embodiments of this invention are not limited to any particular individual feature disclosed here, but include combinations of them distinguished from the prior art in their structures and functions. Features of the invention have been broadly described so that the detailed descriptions that follow may be better understood, and in order that the contributions of this invention to the arts may be better appreciated. There are, of course, additional aspects of the invention described below and which may be included in the subject matter of the claims to this invention. Those skilled in the art who have the benefit of this invention, its teachings, and ""suggestions will appreciate that the conceptions of this disclosure may be used as a creative basis for designing other structures, methods and systems for carrying out and practicing the present invention. The claims of this invention are to be read to include any legally equivalent devices or methods which do not depart from the spirit and scope of the present invention.
The present invention recognizes and addresses the previously-mentioned problems and long-felt needs and provides a solution to those problems and a satisfactory meeting of those needs in its various possible embodiments and equivalents thereof. To one skilled in this art who has the benefits of this invention""s realizations, teachings, disclosures, and suggestions, other purposes and advantages will be appreciated from the following description of preferred embodiments, given for the purpose of disclosure, when taken in conjunction with the accompanying drawings. The detail in these descriptions is not intended to thwart this patent""s object to claim this invention no matter how others may later disguise it by variations in form or additions of further improvements.